An ink jet printer produces images on a receiver medium by ejecting ink droplets onto the receiver medium in an image-wise fashion. The advantages of non-impact, low-noise, low energy use, and low cost operation in addition to the capability of the printer to print on plain paper are largely responsible for the wide acceptance of ink jet printers in the marketplace.
One problem associated with ink jet printing is placement errors of the ink droplets on the receiver medium. Such errors are due to variabilities in the print head manufacturing process in which ink nozzles belonging to the print head are not made identical. The nozzles tend to eject ink droplets in directions different from an ideal direction normal to a nozzle plate in which the nozzles are formed. Such misdirected ink droplet ejection causes misplacement of the ink droplets on the receiver medium. These ink droplet placement errors in turn produce image artifacts (i.e., defects) such as banding, reduced sharpness, extraneous ink spots, ink coalescence and color bleeding.
One method to reduce directional errors in the ejected ink droplets is to minimize the distance between the print head and the receiver medium. Minimizing distance between the print head and receiver medium minimizes error represented by the distance between a correctly placed droplet and a misplaced. This method, however, has its limitations in that if the print head is arranged too close to the receiver medium, there is an increased risk for the ink in the ink nozzles to contact the receiver medium even before ink ejection. When this occurs, the ink spreads-out across the receiver medium in a uncontrolled manner to contaminate the receiver medium.